Vacuum-gap-based lumped element Josephson parametric amplifier

We propose a lumped element Josephson parametric amplifier with vacuum-gap-based capacitor.The capacitor is made of quasi-floating aluminum pad and on-chip ground.We take a fabrication process compatible with air-bridge technology,which makes our design adaptable for future on-chip integrated quantum computing system.Further engineering the input impedance,we obtain a gain above 20 dB over 162-MHz bandwidth,along with a quasi quantum-limit noise performance.This work should facilitate the development of quantum information processing and integrated superconducting circuit design.

Complete-basis-reprogrammable coding metasurface for generating dynamicallycontrolled holograms under arbitrary polarization states

Reprogrammable metasurfaces,which establish a fascinating bridge between physical and information domains,can dynamically control electromagnetic(EM)waves in real time and thus have attracted great attentions from researchers around the world.To control EM waves with an arbitrary polarization state,it is desirable that a complete set of basis states be controlled independently since incident EM waves with an arbitrary polarization state can be decomposed as a linear sum of these basis states.In this work,we present the concept of complete-basis-reprogrammable coding metasurface(CBR-CM)in reflective manners,which can achieve independently dynamic controls over the reflection phases while maintaining the same amplitude for left-handed circularly polarized(LCP)waves and right-handed circularly polarized(RCP)waves.Since LCP and RCP waves together constitute a complete basis set of planar EM waves,dynamicallycontrolled holograms can be generated under arbitrarily polarized wave incidence.The dynamically reconfigurable metaparticle is implemented to demonstrate the CBR-CM’s robust capability of controlling the longitudinal and transverse positions of holograms under LCP and RCP waves independently.It’s expected that the proposed CBR-CM opens up ways of realizing more sophisticated and advanced devices with multiple independent information channels,which may provide technical assistance for digital EM environment reproduction.

Controllable microwave frequency comb generation in a tunable superconducting coplanar-waveguide resonator

Frequency combs are useful in a wide range of applications,such as optical metrology and high-precision spectroscopy.We experimentally study a controllable frequency comb generated in a tunable superconducting coplanarwaveguide resonator in the microwave regime.A two-tone drive is applied on one of the resonance modes of the resonator and comb generation is observed around the resonance frequency of the resonator.Both central frequency and teeth density of the comb are precisely controllable,and the teeth spacing can be adjusted from Hz to MHz.Moreover,we show that a few hundreds of sidebands can be generated using a sufficiently strong drive power and the weakest drive power needed to generate the comb can be reduced to approach the quantum limit.These experimental results can be qualitatively explained via theoretical analysis.

Gatemon Qubit Based on a Thin InAs-Al Hybrid Nanowire

We study a gate-tunable superconducting qubit(gatemon) based on a thin InAs-Al hybrid nanowire.Using a gate voltage to control its Josephson energy,the gatemon can reach the strong coupling regime to a microwave cavity.In the dispersive regime,we extract the energy relaxation time T_(1)~0.56 μs and the dephasing time T_(2)^(*)~0.38 μs.Since thin In As-Al nanowires can have fewer or single sub-band occupation and recent transport experiment shows the existence of nearly quantized zero-bias conductance peaks,our result holds relevancy for detecting Majorana zero modes in thin InAs-Al nanowires using circuit quantum electrodynamics.

Design and fabrication of superconducting transition edge sensor bolometers with background limited noise performance

We successfully designed and fabricated TES bolometers utilizing Al/Ti bilayer TESs as sensitive thermometers.To reduce the intrinsic noise level and tune the saturation power of a bolometer,the TES thermometer is placed on a suspended SiN platform which is thermally coupled to the heat bath by four long SiN beams with different geometries.The measurement results show that the detectors have background limited noise performance,with a low noise equivalent power(NEP)on the order of10-17W/Hz1/2and have a saturation power of several tens pW at a bath temperature of 320 mK.These detectors are suitable for applications in ground-based astrophysics experiments by integrating absorbers for specific wavelengths.

Pt thin-film resistance thermo detectors with stable interfaces for potential integration in SiC hightemperature pressure sensors

Due to the excellent mechanical,chemical,and electrical properties of third-generation semiconductor silicon carbide(SiC),pressure sensors utilizing this material might be able to operate in extreme environments with temperatures exceeding 300℃.However,the significant output drift at elevated temperatures challenges the precision and stability of measurements.Real-time in situ temperature monitoring of the pressure sensor chip is highly important for the accurate compensation of the pressure sensor.In this study,we fabricate platinum(Pt)thin-film resistance temperature detectors(RTDs)on a SiC substrate by incorporating aluminum oxide(Al_(2)O_(3))as the transition layer and utilizing aluminum nitride(AIN)grooves for alignment through microfabrication techniques.The composite layers strongly adhere to the substrate at temperatures reaching 950℃,and the interface of the Al2O3/Pt bilayer remains stable at elevated temperatures of approximately 950 C.This stability contributes to the excellent high-temperature electrical performance of the Pt RTD,enabling it to endure temperatures exceeding 850℃ with good linearity.These characteristics establish a basis for the future integration of Pt RTD in SiC pressure sensors.Furthermore,tests and analyses are conducted on the interfacial diffusion,surface morphological,microstructural,and electrical properties of the Pt flms at various annealing temperatures.It can be inferred that the tensile stress and self-diffusion of Pt films lead to the formation of hillocks,ultimately reducing the electrical performance of the Pt thin-flm RTD.To increase the upper temperature threshold,steps should be taken to prevent the agglomeration of Pt films.

Parity-dependent unidirectional and chiral photon transfer in reversed-dissipation cavity optomechanics

Nonreciprocal elements,such as isolators and circulators,play an important role in classical and quantum information processing.Recently,strong nonreciprocal effects have been experimentally demonstrated in cavity optomechanical systems.In these approaches,the bandwidth of the nonreciprocal photon transmission is limited by the mechanical resonator linewidth,which is arguably much smaller than the linewidths of the cavity modes in most electromechanical or optomechanical devices.In this work,we demonstrate broadband nonreciprocal photon transmission in the reversed-dissipation regime,where the mechanical mode with a large decay rate can be adiabatically eliminated while mediating anti-PT-symmetric dissipative coupling with two kinds of phase factors.Adjusting the relative phases allows the observation of periodic Riemann-sheet structures with distributed exceptional points(Eps).At the Eps,destructive quantum interference breaks both theT-andP-inversion symmetry,resulting in unidirectional and chiral photon transmissions.In the reversed-dissipation regime,the nonreciprocal bandwidth is no longer limited by the mechanical mode linewidth but is improved to the linewidth of the cavity resonance.Furthermore,we find that the direction of the unidirectional and chiral energy transfer could be reversed by changing the parity of the Eps.Extending non-Hermitian couplings to a three-cavity model,the broken anti-PT-symmetry allows us to observe high-order Eps,at which a parity-dependent chiral circulator is demonstrated.The driving-phase controlled periodical Riemann sheets allow observation of the parity-dependent unidirectional and chiral energy transfer and thus provide a useful cell for building up nonreciprocal array and realizing topological,e.g.,isolators,circulators,or amplifiers.